<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>07_面试题2</title>
</head>
<body>
<script>
function fun(n, o) {
    console.log(o)
    return {
        fun: function(m) {
            return fun(m, n)
        }
    }
}

var a = fun(0) // undefined
a.fun(1) // 0
a.fun(2) // 0
a.fun(3) // 0

var b = fun(0).fun(1).fun(2).fun(3) // undefined 0 1 2

var c = fun(0).fun(1) // undefined 0
c.fun(2) // 1
c.fun(3) // 1
</script>
</body>
</html>